As regards mental retardation, a sample survey conducted by the NSSO in 1991 for persons with delayed mental development up to the age of 14 years, estimated that about three per cent suffer from delayed mental development.
En lo que respecta al retardo mental, un estudio de muestras realizado por la NSSO en 1991 sobre personas con retardo mental hasta los 14 años, estimaba que aproximadamente el 3% sufría de retardo mental.